The present invention relates to an optical fiber sensor system.
Japanese Unexamined Patent Publication No. 2008-309776 discloses an optical fiber vibration sensor including a light source, a light receiver, an optical branching and coupling unit having a polarizer, and a fiber loop unit. The light source and the polarizer are optically coupled each other and light controlled so that a polarization state is uniform through the polarizer is output to the fiber loop unit via a coupler. Clockwise light and counterclockwise light propagate into the fiber loop unit. The clockwise light and the counterclockwise light are re-coupled and interfere with each other in the coupler and interference light is obtained. The interference light is received by the light receiver and converted into an electrical signal. When an acoustic signal is applied to the fiber loop, phase differences different from each other are applied to the clockwise light and the counterclockwise light, and the interference state of the interference light changes. The light receiver receives the interference light in which the interference state changes, and therefore stress applied to the fiber loop is detected.